Cancer patients who develop brain tumors (primary and metastatic) need imaging of their tumors with high accuracy and resolution to appropriately analyze the tumors. This imaging can also be used to plan for stereotactic radiosurgery (SRS) treatment. Radiation damage to surrounding brain tissues during SRS treatment is a grave risk. Therefore, there is a need for more accurate imaging technology so patients are appropriately treated and do not need to undergo unnecessary additional radiation treatment.
Current methods of imaging tumors rely on gadolinium-based contrast agents. However, these methods have several shortcomings. First, patients with renal dysfunction cannot use gadolinium (Gd) as a contrast agent because gadolinium injections into the body could cause patients with renal dysfunction to develop nephrogenic systemic fibrosis. Second, there are increasing safety concerns over Gd deposition in the human body such as in the brain. Third, gadolinium-MRIs do not accurately distinguish against what tissue might be a tumor because gadolinium-MRIs only identify cell growths that break the blood brain barrier (BBB). Therefore, Gd-based methods cannot reliably detect the borders of a potential tumor which does not break the BBB. Additionally, Gd-based methods cannot reliably differentiate tumors from other lesions that broke the BBB.
Other potential imaging techniques, such as diffusion-weighted MRI (DWI) and diffusion tensor imaging (DTI), which is a specific imaging technique based on DWI, rely on mapping the diffusion of water molecules to generate contrast in MRI images and identify different tissue microstructures. These techniques, while able to identify areas of interest in the tissue, cannot differentiate between tumors and radionecrosis, which is localized tissue damage caused by exposure to ionizing radiation. Failing to distinguish between radionecrosis and a tumor means that doctors cannot accurately provide treatment without the need for additional follow-up tests to identify which type of tissue the MRI had detected. Further, although SRS treatment is often prescribed for tumors, incorrectly diagnosed SRS treatment can cause further radionecrosis.
What is needed is a non-invasive imaging method to assess cell size and differentiate between radionecrosis and cancerous cells.